Battery charging of an electric vehicle is slow and has high cost with vigorous development of the automotive industry. At present, there are primarily two operating modes of the electric vehicle: plug-in battery charging and battery swapping.
One is plug-in charging mode, that is, the user purchases the electric vehicle including a battery and charges the battery in a charging station or charging pole provided by an operator. Under this charging mode, the user may select slow charging or fast charging by himself/herself as needed. The former has a longer duration but a lower rate whereas the latter has a shorter duration but a higher rate. Charging facilities for the two types of charging are operated by the operators. The operator bills the user according to the electricity consumed during charging. However, after such a charging, the electricity energy discharged by the battery when in use is always less than the electricity energy consumed during the charging process, and a difference between the two depends on the condition of the battery. That is to say, for a given battery with different condition, in the case that the same electricity energy is consumed, a different battery can discharge different electricity energy when in use. Therefore, billing the user only according to the electricity energy consumed during the charging is irrational.
The other one is battery swap mode, that is, the consumer purchases the electric vehicle without the battery but rents or leases the battery from a battery operator, and the user pays by a driving distance of the current battery. However, the driving distance cannot sufficiently reflect the condition of the battery, because it fails to take battery degradation caused by a different usage mode into full consideration and cannot effectively suppress abuse of battery. For example, in two cases where the battery drives the same distance, namely, driven with a heavy load and driven without load, or driven while climbing and driven on flat road, or driven with a variable speed and driven with a uniform speed, battery degradation is different in different cases. Therefore, it is also irrational to bill the user only based on the driving distance.
Therefore, there needs a technique to correctly estimate the condition of the battery, e.g., the degradation degree of the battery, the remaining quantity of electricity energy of the battery, so as to rationally judge a residual value of the battery for the convenience of rational billing.